Tools comprising cubic boron nitride (cBN) are well known in the art. Usually, cBN grains are embedded in a binder matrix which can be e.g. TiN, TiC or TiCN. Aluminum is usually also added, either in metallic form or as an Al-compound.
When making cBN tools comprising a binder matrix of TiN and/or TiCN the binder phase forming powders TiN or TiCN are substoichiometric, i.e. the ratio N/Ti or CN/Ti is substantially lower than 1. These types of powders are difficult to produce with a homogenous composition, and are therefore expensive.
Conventional cBN materials comprising substoichiometric one or more of TiN, TiC and TiCN and Al2O3 have a sintered structure comprising cBN grains, a binder phase of TiC, TiN and/or TiCN grains and Al2O3 embedded into the TiC, TiN and/or TiCN phase. The Al2O3 can be found as isolated spots in the TiC, TiN and/or TiCN phase or adjacent the cBN grains. In the structure, small WC—Co and/or W—Co islands can also usually be seen. This is debris from the milling bodies, which usually are made of cemented carbide.
JP 61-119646 discloses a cBN material having a TiCNO binder phase in the sintered structure.
WO 96/36465 discloses a PcBN or PCD material where a Ti(CNO)z raw material, where z is less than its stoichiometric value, can be used together with a metallic binder phase.
WO2009/150601 discloses a cubic boron nitride material comprising cBN, a binder matrix and a superalloy.
Pre-sintering of cBN materials are known in the art to eliminate some expensive production steps, e.g. brazing. EP1043410 A1 discloses a method for producing PcBN cutting tool inserts. The method comprises the steps of mixing PcBN powder with a liquid and a pressing agent, forming powder agglomerates, and pressing said agglomerates to form a body. The formed body is then subjected to a pre-sintering process to form a porous body which is subsequently subjected to a high pressure-high temperature (HPHT) sintering step to form a dense body.
One object of the present invention is to obtain a method of making a cBN material without using the expensive substoichiometric TiN, TiC and/or TiCN raw materials.
Another object of the present invention is to obtain a cBN material having an increased resistance against crack formation.
It is yet a further object of the present invention to provide a cBN material having an increased tool life.